As known, a sense amplifier is a circuit sensitive to small voltage differences between the signals applied to its two inputs, as function of which it supplies at its two outputs a high-level logic signal, corresponding to the higher voltage input, and a low-level logic signal, corresponding to the other input, or vice versa.
The amplifier power dissipation is both dynamic, in correspondence with the signal transitions, and static during the whole operating time, even though it is implemented in C-MOS technology. Circuits of this type are generally used in static RAM and ROM memories to restore the data stored in differential mode with a small voltage difference between the logic levels. Generally a differential sense amplifier per each bit outgoing from the memory is used; that is why if the datum consists of a rather high number of parallel bits (higher than 16 or 32), the static power dissipation of the set of said circuits becomes considerable.
Presently different types of differential sense amplifiers are known which basically differ from each other in the operation mode. A first kind of differential sense amplifier presents a continuous-time operation, i.e. the circuit is sensitive to all input signal variations, whenever they take place. Hence the sense amplifier presents continuous-time static and dynamic dissipation. Another kind operates in a clocked mode, that is why it is sensitive to all input signal variations which take place during the active phase of clock signal. As a consequence it has a static and dynamic power dissipation only during this phase. Differential feedback sense amplifiers of the latter type exist, which are sensitive to voltage differences between input signals only in correspondence with clock signal transitions, and hence are no longer affected by the successive voltage variations which can take place during the active phase of clock signal. A practical application of such circuits is shown in FIG. 1 of the article entitled "A 9ns 1Mb CMOS SRAM" by K. Sasaki et alii, ISSCC 89 Conference Proceedings, Feb. 15, 1989, San Diego, CA. These differential sense amplifiers have dynamic power dissipation during the transition and a static dissipation for the remaining active phase. Besides the circuits examined show satisfactory operation when the input signals have common mode voltages lower than about 2/3 of the supply voltage.